I just noticed the fastback (fbcache, instant forward and back buttons) feature in Firefox 1.5 no longer works. I created a new profile and verified that it works until the Adblock extension is installed. Even with the extension disables and no filters, it still appears to render or download the pages again when going forward or back a page.

I noticed that Fastback works on my Windows machine at work, but not on my Linux machine at home. I tried removing 0.5.2.056+ and reinstalling 0.5.2.056 and Fastback is only disabled in the 056+ version, at least on Linux.